1 // SPDX-License-Identifier: GPL-2.0 2 #include "reiserfs.h" 3 #include <linux/mutex.h> 4 5 /* 6 * The previous reiserfs locking scheme was heavily based on 7 * the tricky properties of the Bkl: 8 * 9 * - it was acquired recursively by a same task 10 * - the performances relied on the release-while-schedule() property 11 * 12 * Now that we replace it by a mutex, we still want to keep the same 13 * recursive property to avoid big changes in the code structure. 14 * We use our own lock_owner here because the owner field on a mutex 15 * is only available in SMP or mutex debugging, also we only need this field 16 * for this mutex, no need for a system wide mutex facility. 17 * 18 * Also this lock is often released before a call that could block because 19 * reiserfs performances were partially based on the release while schedule() 20 * property of the Bkl. 21 */ 22 void reiserfs_write_lock(struct super_block *s) 23 { 24 struct reiserfs_sb_info *sb_i = REISERFS_SB(s); 25 26 if (sb_i->lock_owner != current) { 27 mutex_lock(&sb_i->lock); 28 sb_i->lock_owner = current; 29 } 30 31 /* No need to protect it, only the current task touches it */ 32 sb_i->lock_depth++; 33 } 34 35 void reiserfs_write_unlock(struct super_block *s) 36 { 37 struct reiserfs_sb_info *sb_i = REISERFS_SB(s); 38 39 /* 40 * Are we unlocking without even holding the lock? 41 * Such a situation must raise a BUG() if we don't want 42 * to corrupt the data. 43 */ 44 BUG_ON(sb_i->lock_owner != current); 45 46 if (--sb_i->lock_depth == -1) { 47 sb_i->lock_owner = NULL; 48 mutex_unlock(&sb_i->lock); 49 } 50 } 51 52 int __must_check reiserfs_write_unlock_nested(struct super_block *s) 53 { 54 struct reiserfs_sb_info *sb_i = REISERFS_SB(s); 55 int depth; 56 57 /* this can happen when the lock isn't always held */ 58 if (sb_i->lock_owner != current) 59 return -1; 60 61 depth = sb_i->lock_depth; 62 63 sb_i->lock_depth = -1; 64 sb_i->lock_owner = NULL; 65 mutex_unlock(&sb_i->lock); 66 67 return depth; 68 } 69 70 void reiserfs_write_lock_nested(struct super_block *s, int depth) 71 { 72 struct reiserfs_sb_info *sb_i = REISERFS_SB(s); 73 74 /* this can happen when the lock isn't always held */ 75 if (depth == -1) 76 return; 77 78 mutex_lock(&sb_i->lock); 79 sb_i->lock_owner = current; 80 sb_i->lock_depth = depth; 81 } 82 83 /* 84 * Utility function to force a BUG if it is called without the superblock 85 * write lock held. caller is the string printed just before calling BUG() 86 */ 87 void reiserfs_check_lock_depth(struct super_block *sb, char *caller) 88 { 89 struct reiserfs_sb_info *sb_i = REISERFS_SB(sb); 90 91 WARN_ON(sb_i->lock_depth < 0); 92 } 93 94 #ifdef CONFIG_REISERFS_CHECK 95 void reiserfs_lock_check_recursive(struct super_block *sb) 96 { 97 struct reiserfs_sb_info *sb_i = REISERFS_SB(sb); 98 99 WARN_ONCE((sb_i->lock_depth > 0), "Unwanted recursive reiserfs lock!\n"); 100 } 101 #endif 102